Process for reducing oxide ores



Patented May 17, 1932 UNITED STATES PATENT OFFICE LYU'IQWIG KERN,FERNANDO C. KERN, AND FREDERICK E. KERN, OF WEBSTER GROVES,

' KISSOURI z PROCESS FOR REDUCING OXIDE ORES Io Drawing.

This invention relates to the reduction of oxide ores, particularlythose of iron, and to the recovery of certain by-products produced inthe process.

Briefly stated, the process comprises mixing finely crushed ore withfinely-divided coal, or other carbonaceous material high in volatiles,plastici'zing and preferably briquetting the mixture, subjecting theplasticized mass 'or briquett'es to destructive distillation in a closedretort with recovery of volatile matter, and thereafter pulverizing thedistilled briquettes and separating the metal therefrom; all as moreparticularly hereinafter described and claimed.

In conventional or known processes of reducing iron ores, alternatelayers of ore, fuel and flux, usually limestone or dolomite, are chargedto a blast furnace and blown with aircto produce the required heat andgases of combustion and to reduce the ore to a metallic state. In suchknown processes coke is employed as the fuel, and consequently, it mustpossess special properties, such as, for example, a content of sulfurand phosphorus. Further, only relatively highgrade ores may be treatedby such processes, i. e., the ore must not contain more than 60 to 65%of substances other than the metal to be recovered and must be extremelylow in sulfur and phosphorus content.

One object of our invention is to provide a process for the reduction ofiron and other metals from their ores, which is applicable tothetreatment of ores higher in sulfur and phosphorus content than thosewhidh may be treated by conventional processes heretofore utilized.

Another object of our invention is to pro.- vide a process by whichcoals or similar carbonaceous materials high in volatile, sulfur andphosphorus content may be employed successfully in-the reduction ofoxide ores.

Another object is to provide a process of the class described, whichdoes not require the use of-fluxes. r

A further object of our invention is the recovery .of volatileby-products produced during the reduction process and also the recoveryof a by-product in the form of coke.

1929. Serial No. 357,831.

A further object of our invention, when the conditioning agents used areeither hydrochloric acid, chlorine, chlorides, or other chlorinecarrying compounds, is the recovery of certain volatile chlorides in thedistillates and their reuse in the system, thereby engenderingproduction economy.

In' accordance with our invention oxide ore is ground fine, preferablyto an extent that Wlll pass through a 50 to 100 mesh screen, and mixedwith raw bituminous coal or other solid bituminous or carbonaceousmaterial, preferably ground to a fineness sufiicient to pass through a100 to 200 mesh screen, the coal or other carbonaceous material beingpreferably of high volatile content and in suflicient quantity toprovide an excess of carbon after the volatiles have been removed. Themixture of ore and coal is now formed into a plastic mass by Wettingwith water or other reagents. Preferably,

the mixture is moistened with hydrochloric acid of from 10 to 20 Baum,the purpose of the hydrochloric acid being to produce plasticity in thecoal and ore mixture and also to react with the sulfur content of theore and coal, with the resultant reduction and/or artial elimination ofsulfur in the form of volatile compounds. In place of hydrochloricacidthere may be employed other acids, chlo-' rine, hypochlorites,salts-especially chlorides, acid salts, or mixtures of salts andacidsespeci'ally chlorides wet with hydrochloric acid, to bring aboutreactions with sulfur and phosphorus and o impart sufficient plasticityto the mixture. Also in the treatment of ores or mixtures high inphosphorus there may be employed bases, basic .salts or mixtures ofbases and salts to likesimilar homogenizing apparatus, and fur thertreated, as hereinafter set forth. Themass is preferably molded intobricks or briquettes or other shaped objects by means of a suitablebriquetting machine, such as is 600 C. to drive off the volatiles, whichare recovered by condensation in a known manner. The products thusrecovered are light and middle oils and also some heavier fractions, andthe non-condensible gas thus formed is a high calorific coal gascontaining some carbon monoxide, carbon dioxide and nitrogen compounds,which may be recovered and utilized. Upon completion of the distillationthe temperature'is raised sufficiently to allow the residual carbon orcoke to react with the remaining oxygen in the oxide ore to form carbonmonoxide and/ or carbon dioxide and reduce the ore. If the temperaturesare maintined at or above 900 C., the chief gas eliminated will becarbon monoxide, which may be collected and utilized for heatingpurposes. In this heating process further nitrogen compounds are givenoff, chiefly in the form of ammonium chloride. Other volatile chloridesare' also evolved. These chlorides are preferably recovered and used asconditioning agents for the plasticizing operation. On account of thetemperatures maintained and the' intimate contact of the carbonaceousand bituminous matter with the finely-divided mineral matter of the mix,

these carbonaceous and bituminous materials are so decomposed as toleave a peculiarly reactive carbon residue known as active carbon todistinguish it from the less reactive form commonly found in ordinarycoke.

Throu h expulsion of the liquid and gaseous products from the coal, andon account of the intimate contact of the coal and the oxide oreengendered by the homogenizing or its close contact with the ore,efi'ectively reduces the latter to the metallic state by breaking downthe combination of metal and oxy-' gen. When sulfur-containing coals areemployed, such as the Illinois bituminous coals, the sulfur reacts alsowith the chlorine liberated from the chlorides introduced as such orformed through the reaction of the hydrochloric acid, chlorine, etc.,with the basic substances or impurities present in the gangue material,as well as in the ore, and the sulfur is thus removed as volatilecompounds,

largely in the form of hydrogen sulfide and sulfur chlorides.

The residue of the distillation or carbonization now comprises, inbriquette form, a

mixture of desulfurized and devolatilized 9 coke and reduced metal freeof sulfur and phosphorus, and containing silicious, calcareous andaluminous constituents of both the ore and coal which have not beenvolatilized as chlorides. To recover the reduced metal the briquettesare crushed and pulverized and the metal separated by known mechanicalmethods.

The material separated from the reduced metal constitutes a commerciallyvaluable byproduct, the recovery of which brings about a considerablesavings in the reduction process above described. This material consistsmainly of a mixture composed of de-volatilized or carbonized coal orcoke, and more or less gangue material. This mixture of coke and ganguematerial may be used as a fuel for steam boilers or other furnaces, orfor making water gas. It is of special value in the manufacture of watergas, as the gangue material consists essentially of silica, which actsas a catalyst in water gas reactions. Where the gauge materialassociated with the coke is present only in negligible quantities, thecoke may also be used as a domestic fuel. On the other hand, if thegauge material is present in such quantities as to make the use of thecoke prohibitive for certain purposes, the mixture may be subjected toair flotation, or to wet flotation to separate the gangue material fromthe carbon. The resultant product of such treatment is a comparativelypure carbon of high calorific value, low in ash and volatile, and is anexcellent sulfur-free steam coke having the property of igniting rapidlyand at low combustion temperatures. It may be advantageously used forheat, light and power purposes, or for preparing activated carbon.

In order that the details of our invention may be better understood, aspecific example of the process will be described, although it is to beunderstood that the invention is not limited to the particular materialtreated or to the specific conditions of operation set forth.

Soft red hematite ore containing approximately 44% iron, 17% silica, 1%sulfur and 3.7% alumina is ground together with a high volatilebituminous coal containing volatile matter and 3% sulfur, the proportionbeing by weight of ore to 40% by weight of coal. The mixture is wettedin wet pans with 10 Baum hydrochloric acid, sufiicient in amount toreact as described and to produce a plastic mass, and the mixture formedinto briquettes. The briquettes are then dried and distilled attemperatures below 600 C. for about five hours, after which thetemperature is raised to between 900 and 1,000 0., the tem erature beingmaintained until evolution 0 carbon monoxide ceases. The condensablevolatile matter from the low temperature treatment and the gaseousmaterials from the subsequent heating are removed, collected andutilized as above set forth. The residue resulting from the heattreatment is cooled, finely ground and passed over a magnetic separatorof known construction for separation of the metallic iron. The iron thusobtained is of'suflicient purity to be used directly in an electricfurnace for the production of steel or for other purposes. The residualmaterial remaining after the removal of the iron may be utilizeddirectly as fuel or in the production of water gas, or as abovedescribed.

From the foregoing it will be seen that we have devised a novel processfor reducin oxide ores, especially iron oxides, in whic commerciallyvaluable by-products are recovered in the form of oils, gases and solidfuel. Also by virtue of the procedure above described,- it is possibleto treat, according to' our process, ores of lower metal content and ofhigher sulfur and phosphorus con-. tent than commercially possibile byprocesses now utilized. Further, in place of a coke free of volatiles,sulfur, and phosphorus,

such as heretofore employed, we may use inour process coals andcarbonaceous materials ,high in volatiles, sulfur, and phosphorus.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. The process of reducing oxide ores, which comprises forming a mixtureof comminuted ore, comminuted solid distillable carbonaceous material,and a chlorine containing material plasticizing the mixture, forming thelastic mixture into briquettes, heating the riquettes out of contactwith air sufficiently to distil the volatiles and to reduce the ore tothe metallic state, and recovering the metal from the solid residue.

2. The process of reducing oxide ores, which comprises mixing the orewith a solid bituminous or carbonaceous material, wetting the mixturewith chlorine-containing agents adapted to react with the impuritiespresent in the carbonaceous substance and oxide ore, molding andpressing the mass to form briquettes, heating to dry said briquettes andthereafter subjecting said briquettes to heat out of contact with air,at a temperature sufiiciently high to volatilize chlorides formed asWell as at least part of the hydrocarbons obtainable from the coalcollecting the products of volatilization, raising the temperaturesufliciently to reduce the ore to its metallic state, and recovering themetal from the solid residue of carbonization.

3. The process of reducing oxide ores, which comprises mixing the orewith solid distillable carbonaceous material, wetting the mlxture with areagent adapted to react upon sulfur and whereby said sulfur andphosphorous are substantially eliminated from the mixture, forming themixture into briquettes, heating the bnquettes out of contact with airto a distillation temperature to remove volatile matter, raising thetemperature sufiiciently to reduce the ore to the metallic, state,and'recovering the metal from the solid residue.

4. The process of'recovering metalsfrom their oxide ores which,comprisesmixing the ore with solid distillable carbonaceous'material,wetting the mixture with a reagent adapted to produce chlorine onheating, forming the mixture into briquettes, subjecting the-briquettesto destructive distillation in a-closed retort, raising the temperaturesufficiently to reduce the ore to the metallic state, and separating themetal from the solid residue.

5. The combined process of separating metals from their oxide ores andrecovering volatiles from distillable carbonaceous material, whichcomprises mixing the ore with the distillable carbonaceous material,wetting the mixture with hydrochloric acid, forming the mixture intobriquettes, subjecting the briquettes to Idffitructive distillation in aclosed retort, re oving and collecting the resultant vapors, raising thetemperature sufiicientlg to reduce the ore to the me tallic state, anseparating the metal from the resultant residue.

6. The process of recovering iron from its oxide ores, which comprisesformin a mixture of the ore, bituminous coal, an a chlorine-containingmaterial, forming the mixture in a plastic mass, heating the mass in aclosed chamber sufliciently to expel vapors and gases and to reduce theiron oxide to metallic iron, and separating the iron from the solidresidue.

7. The process of recovering iron from its oxide ores, which comprisesmixing theore with bituminous coal, wetting the mixture with a reagentadapted to produce chlorides on heating, forming the mixture intobriquettes, destructively distilling the briquettes and recovering theresultant vola-- tiles, raising the temperature sufliciently to reducethe iron oxides to metallic iron, and separating the iron from the solidresidue.

8. The process of recovering iron from its oxide ores, which comprisesmixing the ore with bituminous coal, plasticizing, the mixture by meansof hydrochloric acid and forming the plastice mass into briquettes,-

heating the briquettes sufficiently to reduce the iron oxides tometallic iron, and separating the iron from the solid residue.

phosphorous upon heating, I

9. The process which comprises mixing comminuted iron oxide withcomminuted bituminouscoal, wetting the mixture with hydrochloric acidforming the mixture into briquettes, destructively distilling thebriquettes in a closed retort, removing and condensing the resultantvapors, further heating the briquettes sufliciently to reduce the ironoxides to metallic iron and collecting the resultant gases, pulverizingthe briquettes, and se arating the same into metallic. iron and co e.

10. The process of reducing oxide ores containing phosphorus, whichcomprises mixing the ore with solid distillable, carbonaceous material,Wetting the mixture with a reagent adapted to convert the phosphorousinto compounds of phosphorus, forming the mixture into briquettes,heating the briquettes sufficiently to drive ofi volatiles and to reducethe ore to the metallic state, and separating the metal from thebriquettes.

11. The process of reducing iron ore containing phosphorus, whichcomprises mixing the ore with bituminous coal, plasticizing the mixtureby means of a reagent adapted to convert the phosphorus into compoundsof phosphorus, forming the plastic mass into briquettes, destructivelydistilling the briquettes and recovering the resultant volatiles,raising the temperature sufliciently to reduce the iron oxides tometallic iron, pulverizing the briquettes, and separating the irontherefrom.

12. The process as described, which comprises the steps consisting ofcomminuting an oxide ore and bituminous coal to a fine state ofdivision, mixing same and adding to a chlorine carrier, homogenizing thethree components to form a cohesive and plastic mass, having a closecontact, increasing the' contact by pressing the mass to form shapes ofdesired size, heating said shapes to evaporate water present, increasingthe temperature to drive ofi from said mass the chlorides formed by theco-action of the chlorine carrier and the basic salt-forming impuritiespresent, and to likewise drive 011' a substantial amount of condensableand non-condensable hydrocarbons, likewise hydrogen,

carbon monoxide, etc., from the mixture, re-

covering said condensable and non-condensable products ofvolatilization, exposin the ore-coal compound to heat, sufficiently tobring about the conversion of the oxide ore into its metallic state andthe coal into coke, and separating the reduced ore and coke obtained.

13. The process of reducing oxide ores which comprises mixing comminutedore with comminuted distillable carbonaceous material, plasticizing andhomogenizing the mixture with a chlorine-containing agent, forming theplastic mixture into briquettes, distilling the briquettes to remove thevolatiles therefrom, and heating the'distilled briquettes to reduce theore to the metallic state.

14. The process of reducing oxide ores which comprises forming a plasticmixture of comminuted ore, oomminuted distillable material, and achlorine-containing reagent, forming the plastic mixture intobriquettes, distilling the briquettes to remove the volatiles therefrom,and heating the distilled briquettes to reduce the ore to the metallicstate.

15. The process of reducing oxide ores Y

